Traditionally, a wafer as a substrate is subjected to various processing steps to manufacture semiconductors. With further advancement in higher integration of elements and miniaturization of circuits in recent year, there is a demand for maintaining a high cleanliness level of environment surrounding wafers, so as to avoid adhesion of particles or moisture on the surface of a wafer. Further, in order to avoid a change in the characteristics of the surface, such as oxidation of a wafer surface, a wafer-surrounding environment is made an atmosphere of nitrogen which is an inert gas, or made vacuum state.
To properly maintain the atmosphere around the wafer, the wafers are placed inside a sealed storage pod called FOUP (Front-Opening Unified Pod), and nitrogen is filled in the inside thereof of the pod. Further, for transferring wafers between a processing apparatus which processes wafers and the FOUP, air EFEM (Equipment Front End Module) is used. The EFEM structures a wafer conveyance chamber which is substantially closed inside a casing. One of wall surfaces facing each other has a load port that functions as an interface unit with the FOUP, and the other wall surface is connected to a load lock chamber which is a part of the processing apparatus. Inside the wafer conveyance chamber, a wafer conveyance apparatus configured to convey wafers is provided. Wafers are loaded and unloaded between the FOUP connected to the load port and the load lock chamber.
As a load port, for example, PTL 1 suggests a structure in which the door unit protrudes from the casing towards the FOUP.